The prior art is replete with apparatuses for measuring rate of air flow, sensing rate, acceleration, and the like by using thermistors (U.S. Pat. No. 3,500,691; U.S. Pat. No. 3,628,371 and U.S. Pat. No. 3,631,729); by electrically accelerating ions of one polarity toward an ion collector or counter (U.S. Pat. No. 3,910,122 and U.S. Pat. No. 3,910,123); or by passing an electrically conductive fluid into a divider which splits the fluid and enters a portion of fluid into one electrolytic chamber with the other portion entering a second electrolytic chamber, the comparative portions depending on the acceleration transverse to the flow of fluid (U.S. Pat. No. 3,163,048). All of these techniques have, however, been encumbered by disadvantages that have rendered them less than optimal.
Assembly of sensors employing thermistors has proven to be difficult because accurate placement of very small thermistor beads is required. Also, the thermistor elements have been shown to be susceptible to damage by shock and vibration--a significant drawback in aircraft applications. In addition, long-term changes in calibration have been noted as the characteristics of the heated beads change. Further, ambient temperature and pressure changes as well as transient shifts resulting from heat transfer problems during turn on have also affected the performance of such devices.
The use of platinum wires instead of thermistors, which has also been proposed in the prior art, has required amplifiers and thermal compensation elements for the amplifiers, thereby adding to the complexity of the thermal device.
Those prior art techniques which teach the electrical acceleration of single polarity ions towards an ion collector or one of a plurality of ion collectors require sensitive circuitry for extracting ions of one polarity from a pool of ions of either polarity and delicate electrode elements for accelerating the ions like a "gun". Such apparatuses thus include a source of ions, means for separating out the ions of one polarity, means, generally cathodes and electrodes, for electrically accelerating that one polarity of ions, and means for collecting or counting the ions. The present invention obviates the need for the second and third means required by the prior art and provides for less complicated apparatus for the last means.
Measuring the volume of flow into two chambers, wherein an electric current induced through the fluid in each chamber measures Coriolis acceleration transverse to the flow, suffers from several shortcomings. First, impurities in the fluid will have severe effects on conductivity and, second, the variety of fluids which can be used are limited.